Trout Preliminary Hints And Advice
The amateur who is beginning trout culture had better by all means buy
eyed ova from a fish cultural establishment. There are many of these in
the British Isles, and nowadays eyed ova are packed and sent safely all
over the country. The artificial spawning of trout is not an undertaking
in which the beginner is likely to achieve great success, and therefore
I should advise him to avoid relying upon it when he commences his
operations as a fish culturist.
Collecting the ova of wild trout is also an operation of some
difficulty, and lays the beginner open to much more disappointment than
if he deals with eyed ova purchased from a reliable establishment.
Instead of having to watch and care for the ova through a critical and
dangerous period, he receives them shortly before the young fish hatch
out, when the ova are not in the most delicate stage.
It is of the greatest importance that everything should be ready for the
ova long before they are expected, as hurry and new apparatus are likely
to cause failure. Any concrete and varnished or enamelled woodwork
should be exposed to the action of a current of water for at least five
or six weeks before they are brought into actual use.
The choice of a suitable spot in which to make his hatchery is a serious
point for the consideration of the amateur. A spring is the best water
supply as a rule, for the water is usually of a fairly even temperature,
and does not require filtering, but water from a stream where trout are
known to live is quite safe. A few years ago it would have been
necessary for any one wishing to take up fish culture, to erect a
building in which to place his hatchery if he intended to hatch any
number of eggs, in order to guard against frosts. At the present time,
the eyed ova of even the brown trout (_Salmo fario_) can be obtained
sufficiently late to be safe against a frost severe enough to cause any
damage, and as the rainbow trout (_Salmo irideus_) spawns in February
and March, the amateur is, at the time he receives the eyed ova, quite
safe from frost.
The best method to pursue is to make long narrow ponds, with a current
running through them, and to hatch the eggs out in trays and boxes
suspended in these ponds. When the young fish hatch out, the trays which
contained the ova can be removed, and the young fish kept in the boxes.
Later on the young fish can be released from the boxes into the ponds. I
shall subsequently describe how these ponds, trays, and boxes should be
The rearing ponds should be made, if possible, at a fall in the level of
the water supply, so that they may be easily emptied. This is an
important point which is frequently overlooked by amateurs. There should
be an outlet on a level with the bottom of the pond, and if the water
escapes through a pipe, that pipe should incline downwards. This, in a
series of ponds, of course necessitates the ponds being at different
levels, but the water is thus under much better control than if the
outlet is at a higher level, and the ponds are easily emptied. Ponds
may, however, be worked successfully with the outlet in mid-water, or
even near the surface, though this does not ensure such a certainty of
change of water throughout the pond. It is not, however, always possible
to obtain such a difference in level between the supply and waste. In
such cases the ponds should be made shallower near the outlet.
A popular idea seems to be that a gravel bottom is necessary for the
well-being of trout; this is quite a mistake. Personally, I believe that
a good earth bottom is best in a rearing pond, and even in a pond lined
with concrete I should always put a layer of mould, preferably turf
mould, at the bottom. With the use of this mould during the subsequent
operations in rearing trout I shall deal later on.
The size of the ponds, of course, depends upon the number of trout to be
reared. It is better to have several medium sized ponds than one large
one, as then accident or disease occurring in a pond will only affect a
portion of the stock of fish. Mr. J. J. Armistead in _An Angler's
Paradise, and How to Obtain It_, says: "A pond sixty feet long, four
feet wide, and about three feet deep, will hold ten or fifteen thousand
fry at first, and give them plenty of room to grow, but by the end of
July the number should be reduced to five thousand, which may be left
till October, when they should again be thinned out, or, better still,
put into larger pond."
I should advise the amateur who is dealing with only a few thousand fish
to work on a smaller scale in these proportions, and to make these
changes gradually, and yet more gradually as the season advances. That
is to say, work with a third of the number of fry in ponds half the size
and move some fish several times before the end of July. As October
approaches, make changes of smaller numbers of fish more frequently.
Late in the autumn is, in my opinion, the best time to put the young
fish into the water they are to inhabit permanently. It must be a
mistake to rear them artificially longer than is necessary, and by the
end of November they should be fairly capable of looking after
Trout, which are artificially reared on chopped meat and other soft
foods, suffer from a lack of development in the stomach walls, and also,
probably, in the rest of their digestive apparatus. The first case I saw
of the stomach of an artificially reared trout was a two-year-old
trout, upon which Dr. C. S. Patterson performed an autopsy. The stomach
walls were as thin as a sheet of tissue paper. At the time I believed,
and, if I remember rightly, he also thought that this was due to
atrophy, but I am inclined to think that this idea was only partially
correct. The stomach walls of the autumn yearling trout, which is
artificially reared on soft food, do not show any marked abnormality in
the way of thinness; but as the trout's age increases, so does the
thickness of the stomach wall decrease in proportion to its size. This
leads me to believe that the development of the stomach wall, at any
rate, and probably also of the glands secreting the gastric juice and
the digestive apparatus generally, gradually ceases when at about the
age of eight or nine months if the trout is fed upon soft food.
Probably, also, a certain amount of atrophy and dilatation of the
stomach wall is produced. If my observations are correct, so also is the
conclusion that a trout which cannot digest hard food, of which a great
part of his natural food consists, will not have a really fair chance
when turned out. Therefore, I say, turn out your trout in November,
unless you can feed them on such food as shrimps, snails, bivalves and
_Corixae_; and if you stock with "ready made" fish, stock with yearlings
in the late autumn.
The turning out of his fish in November will also allow the amateur
plenty of time to prepare his ponds and apparatus for next year's
operations. If the ponds are made on a stream, probably the very best
place that can be chosen is where there is a fairly sharp bend in the
stream just below a fall. An artificial fall can often be made where the
banks are high by damming up the stream several feet. Care must be
taken, however, to avoid any risk of the ponds being flooded.